Hierarchically Periodic Macroporous CdS–ZnO Heterojunctions with Multiple Quantum Well-like Band Alignments for Efficient Photocatalytic Hydrogen Evolution without a Cocatalyst

Abstract

Heterostructures constructed by conventional methods, particularly those randomly distributed manner on the catalyst surface as well as forming core−shell structures, lead to imbalance in carrier utilization, limitation of charge extraction/transfer, and hindrance of light harvesting. In this study, we constructed a new type of heterostructure consisting of alternate CdS and ZnO grains bridged with good interfaces in the hierarchically periodic macroporous (HPM) walls by the pyrolysis of CdZnS solid solution in a polymethyl methacrylate nanoreactor. Since the alternately arranged CdS−ZnO heterojunctions in the HPM form multiple quantum well-like (MQW-like) band alignments that favor the Z-scheme charge transfer, the photogenerated electrons and holes are spatially separate and accumulated on CdS and ZnO parts, respectively. Besides the desirable spatial separation of the photogenerated charges, the enabled excellent mass transfer in the macroporous structures effectively accelerates the utilization of the carriers. Owing to the synergistic effect of the MQW-like band alignments and the HPM structures, the photocatalytic H 2 evolution rate of HPM CdS−ZnO is as high as 587.8 μmol h −1 without a cocatalyst. This work introduces a fascinating strategy for the creation of alternate heterojunctions to improve carrier utilization.

Triptycene-Based Polymer-Incorporated CdxZn1–xS Nanorod with Enhanced Interfacial Charge Transfer for Stable Photocatalytic Hydrogen Production in Seawater

“…Besides, the XRD patterns of TCP@Cd x Zn 1−x S (x = 0.2, 0.4, 0.6, and 0.8) were investigated and are displayed in Figure S1. Solid-state 13 C NMR shows the delicate chemical structures of TCP and TCP@CZS in Figure 1b. In comparison to TCP, the TCP@CZS composite exhibits the same characteristic peaks at 54 ppm (bridging carbons derived from triptycene unit), 139 (144) ppm (the aromatic carbons of triptycene), and 123 (127) ppm (aromatic carbons of boronic acid), verifying the successful preparation of the composite.…”

“…Characterization. 13 C CP/MAS NMR spectra were carried out via a Bruker AVANCE III 300 MHz spectrometer. The core−shell structure of TCP@CZS was analyzed by an X-ray diffractometer (D/ max 2500PC) equipped with Cu Kα radiation.…”

“…Construction of noble-metal-free catalysts with solar-driven H 2 generation in natural seawater is considered as a promising way to solve the shortage of energy. − In recent years, Cd x Zn 1– x S as a bimetal solid solution has attracted considerable attention due to its tunable/suitable band gap, excellent photoelectric properties, and low cost, in which bimetal chalcogenide usually shows higher H 2 production activity than single metal sulfide (CdS and ZnS). − For instance, ZnS needs to be activated by UV light, which reduces the utilization of visible light . By adjusting the value of x in Cd x Zn 1– x S, the range of the band gap can be changed to compensate for the deficits of CdS and ZnS. , In spite of the Cd x Zn 1– x S solid solution with a good H 2 evolution rate, it still suffers from severe photocorrosion in seawater as well as rapid charge recombination.…”

“…(a) XRD patterns of TCP, Cd 0.6 Zn 0.4 S, and TCP@CZS. (b)13 C CP/MAS NMR spectra of TCP and TCP@CZS-3.…”

Peanut‐Like Zn0.5Cd0.5S/BiVO4 S‐Scheme Heterojunction Photocatalysts Toward Optimized Visible Light Photocatalytic Performance

“…[18][19][20][21][22][23] Photocatalytic materials often suffer from low efficiency due to factors such as poor carrier mobility, short carrier diffusion length, poor interfacial carrier selectivity, and poor electrochemical kinetics. [24] To address this, the construction of heterostructures is an effective method. Among them, the Z-scheme heterostructure has been widely studied and is representative, as it can prolong the life of photogenerated charges, improve the mobility of carriers, prevent the reverse transport of electrons and holes, improve the selectivity of the interface, and broaden the range of light absorption, thus improving the photocatalytic material's energy utilization efficiency.…”